High impact strength thermoplastic resin is prepared by mixing the styrene-acrylonitrile copolymer with rubber particles. In general, the high impact strength thermoplastic resin is prepared by graft-copolymerization of styrene and acrylonitrile in the presence of rubber and by mixing the graft product with hard matrix resin containing another styrene-acrylonitrile copolymer.
The high impact strength thermoplastic resin exhibits different characteristics according to the used rubber. The rubber that has been added to the acrylonitrile-butadiene-styrene (ABS) polymer is the butadiene polymer.
The ABS polymer has excellent impact strength even at a very low temperature but poor weather resistance and aging resistance. Thus, to produce a resin with excellent impact strength and at the same time excellent weather resistance and aging resistance, it is essential to eliminate the unsaturated ethylene polymer from the graft copolymer. Therefore, the acrylate-styrene-acylonitrile (ASA) polymer cross-linked with the alkyl acrylate rubber polymer is preferred. The ASA polymer has been widely applied to glossy colored outdoor products including garden furniture, boat, land mark, street light cover, etc.
German Patent No. 1,260,135 describes the preparing method of the ASA polymer having excellent weather resistance and aging resistance. The core used for the ASA polymer is 150˜800 nm in mean diameter and is a cross-linked acrylate large-caliber polyacrylate latex with narrow size distribution. The polymer containing the large-caliber polyacrylate latex exhibits enhanced notched impact strength, higher hardness and reduced contraction, compared with the polymer containing the small-caliber polyacrylate latex. However, the large-caliber graft copolymer has problems of poor levels of gloss and scratch resistance, compared with the small-caliber graft copolymer.
According to U.S. Pat. No. 6,448,342, a monomer comprising aromatic vinyl compound, vinyl cyan compound and alkyl methacrylate is graft-copolymerized in the presence of butadiene rubber particles and then the terpolymer comprising aromatic vinyl compound, vinyl cyan compound and alkyl methacrylate is used as a hard matrix to produce butadiene-based rubber-reinforced thermoplastic resin composition for laser marking having excellent transparency and white chromogenic property. The transparent butadiene-based rubber-reinforced thermoplastic resin has excellent gloss and scratch resistance but reduced weather resistance and impact resistance.
One of the problems of the conventional resin compositions is the unbalance among properties, such as impact-resistance, weather resistance, gloss and scratch resistance, meaning that this property is excellent but the other property is poor.